potential data loss bug in ZFS on Linux 0.7.7

BLinux

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for anyone using latest ZFS on Linux, I think you'll want to know about this bug:

Unlistable and disappearing files · Issue #7401 · zfsonlinux/zfs

highlights: although this bug is easily reproduced on CentOS/RHEL distros, it also affects Ubuntu and others. people have found ways to trigger this bug in non-CentOS/RHEL OSes now...

on CentOS 7, to revert back to 0.7.6, i've confirmed this command works:

$ yum downgrade kmod-spl kmod-zfs libnvpair1 libuutil1 libzfs2 libzpool2 spl zfs

this was a clean install with 0.7.7 installed, not upgraded from previous, and I confirmed I can downgrade with the above command.
 
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gigatexal

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for anyone using latest ZFS on Linux, I think you'll want to know about this bug:

Unlistable and disappearing files · Issue #7401 · zfsonlinux/zfs
Seems only to affect RHEL and then those from the repos as building it from source on Ubuntu doesn’t show this issue.

Also yum is transactional I had no idea you could do this:

For reverts, I usually do:

$ yum history (identify transaction that installed 0.7.7 over 0.7.6; yum history info XXX can be used to confirm)
$ yum history undo XXX (where XXX is the transaction number identified in the previous step)
Note that with dkms installs, after reverts, I usually find I need to:

$ dkms remove zfs/0.7.6 -k `uname -r`
$ dkms remove spl/0.7.6 -k `uname -r`
$ dkms install spl/0.7.6 -k `uname -r` --force
$ dkms install zfs/0.7.6 -k `uname -r` --force
To make sure all modules are actually happy and loadable on reboot.


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BLinux

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yeah, downgrade is easy. and even if you installed straight to 0.7.7 (without upgrading from previous version), you can downgrade with:

yum downgrade kmod-spl kmod-zfs libnvpair1 libuutil1 libzfs2 libzpool2 spl zfs

and it will take you to 1 version eariler as long as the RPMs are available in the repo.
 
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gigatexal

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yeah, downgrade is easy. and even if you installed straight to 0.7.7 (without upgrading from previous version), you can downgrade with:

yum downgrade kmod-spl kmod-zfs libnvpair1 libuutil1 libzfs2 libzpool2 spl zfs

and it will take you to 1 version eariler as long as the RPMs are available in the repo.
That’s really hella cool. Is there a Ubuntu/Debian feature that does the same?


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BLinux

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sounds like they are about to pull the 0.7.7 RPMs and will release a 0.7.8. current recommended course of action is to downgrade to 0.7.6 until this is fixed and 0.7.8 is released.
 

BLinux

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latest update: they've reproduced this bug on other non-RHEL/CentOS distros... so if using ZoL on Ubuntu or others, you need to take precautions too...
 

BLinux

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@Patrick @cliffr : you might want to update the article as other OSes are also affected. the statement "It seems that users of Ubuntu among others may be safe from this one" is no longer true...
 
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PigLover

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Note that you don't get ZFS 0.7.7 as part of Ubuntu. With the last official release (17.10) they only packaged ZFS 0.6.x (I think 0.6.5) and even though it's not released officially for a couple more weeks the 18.04/Bionic packages only include ZFS 0.7.5. There are unofficial repositories (PPAs) and the self-build option to get ZFS 0.7.7. But an Ubuntu user using the "official" packages from Canonical isn't at risk because they never integrated the buggy release.

Lots of Proxmox users here too - I believe (need to check, can't VPN my lab right now) Proxmox 5.1 includes ZFS 0.7.2.